Segment Information - Schedule of Segment Information (Detail) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2019	Dec. 31, 2018	Dec. 31, 2017
Segment Reporting Information [Line Items]
Total revenues	$ 2,404	$ 2,524	$ 2,470
Depreciation and amortization	377	372	350
Total interest charges	134	118	119
Provision for income taxes	77	81	197
Net income	370	341	316
Total assets	10,007	9,155	8,364
Capital expenditures	1,283	1,109	640
Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	2,404	2,524	2,470
Sales to Affiliates [Member]
Segment Reporting Information [Line Items]
Sales to affiliates	0	0	0
Eliminations [Member]
Segment Reporting Information [Line Items]
Total revenues	(22)	(30)	(22)
Depreciation and amortization	0	0	0
Total interest charges	0	0	0
Provision for income taxes	0	0	0
Net income	0	0	0
Total assets	(593)	(487)	(555)
Capital expenditures	0	0	0
Eliminations [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	0	0	0
Eliminations [Member] | Sales to Affiliates [Member]
Segment Reporting Information [Line Items]
Sales to affiliates	(22)	(30)	(22)
Tampa Electric [Member]
Segment Reporting Information [Line Items]
Total revenues	1,965	2,066
Tampa Electric [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	1,965	2,066	2,054
Depreciation and amortization	336	312	300
Total interest charges	117	102	104
Provision for income taxes	59	65	171
Net income	316	294	273
Total assets	9,007	8,235	7,635
Capital expenditures	1,055	940	518
Tampa Electric [Member] | Operating Segments [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	1,961	2,063	2,052
Tampa Electric [Member] | Operating Segments [Member] | Sales to Affiliates [Member]
Segment Reporting Information [Line Items]
Sales to affiliates	4	3	2
PGS [Member]
Segment Reporting Information [Line Items]
Total revenues	461	488
PGS [Member] | Operating Segments [Member]
Segment Reporting Information [Line Items]
Total revenues	461	488	438
Depreciation and amortization	41	60	50
Total interest charges	17	16	15
Provision for income taxes	18	16	26
Net income	54	47	43
Total assets	1,593	1,407	1,284
Capital expenditures	228	169	122
PGS [Member] | Operating Segments [Member] | Revenues - External [Member]
Segment Reporting Information [Line Items]
Total revenues	443	461	418
PGS [Member] | Operating Segments [Member] | Sales to Affiliates [Member]
Segment Reporting Information [Line Items]
Sales to affiliates	$ 18	$ 27	$ 20